Since the 'CJet' is still just a 'paper airplane', can you really say for sure that it's seat/mile cost will be less than the 737-700/-800?
It's about as much of a paper airplane as the A350 is (if not less so). They have awarded engine and avionics contracts to various suppliers and development of this plane has been well underway for at least 5 years and was originally envisioned as EJet competition. Now it looks like a really viable DC9/-80/A319 replacement aircraft. The transmission in a turbine which would significantly improve engine efficiency, extensive use of composites (etc.) all help to contribute to the fuel savings. The board is expected to give the CJet the go ahead this summer with NWA as the likely launch customer (so say the rumors). Expect prototypes flying sometime around 2011 with the plane entering service around late 2012/early 2013.